The present invention relates to communication systems and communication methods in which users having different connection environments are connected with each other through the optimum communication means automatically selected so as to make the optimum smooth communication, and also to terminal devices, computer programs for communication, and computer-readable recording media having the communication programs recorded thereon.
In recent years, with the progress of communication techniques, communication lines having various transmission bands have been developed and put in practical use. For example, well known are an ISDN (Integrated Services Digital Network) line with its transmission rate of 128 kbps, a T1 line with its transmission rate of 1.544 Mbps, an ADSL (Asymmetric Digital Subscriber Line) with its up transmission rate of 16 kbps to 1 Mbps and its down transmission rate of 1.5 to 8 Mbps, and a cable television (CATV) communication line with its transmission rate of 512 kbps. Using one of such communication lines, each user connects his or her client terminal device with an Internet service provider (ISP) or the like to receive desired services or provide predetermined services.
On the other hand, as communication means capable of making a one-to-one communication between persons or communications among several persons on a network, there are a text chat system for which even a connection environment of a transmission band with a transmission rate of about 56 kbps suffices, an Internet telephone system using VOIP (Voice Over IP), a video chat system and a voice chat system that require a connection environment of a transmission band with a transmission rate of about 128 kbps, TV conference systems that require a connection environment of a transmission band with a transmission rate of about 512 kbps, and so on.
In general, users have different connection environments as described above. In addition, it is difficult for users who intend to have communications with each other to know the connection environments of the opposite parties. Thus, there is a conventional problem that such users cannot select the optimum communication means for their communication.
For example, in a case in which the users each have a connection environment of a high-speed communication line such as the T1 line or the like described above, they need not communicate through the text chat system that uses a narrow band communication line. They can communicate through the video chat system or the like that requires a communication line of a broader transmission band than the text chat system. If they nevertheless adopted communication means for a narrow band communication line, it means that their valuable high-speed communication line was not being utilized effectively and it never means that they had a fully smooth communication.